Retractable cord reels have been used in various applications to retractably store various types of cables. Typically, a reel might have a stationary end and a retractable end, the retractable end capable of extension from and retraction back into the reel, and a stationary end that does not move during extension or retraction. Such a configuration reduces the mess typically associated with loose wires, as well as dangers related to loose cords, hazardous operating environments and the like.
In one prior art retractable reel, the extendable and stationary portions of a cord may be separate, but may be connected for example by brush-like contacts. The brush-like contacts slide along the inside or outside of the rotating spool, effectively maintaining a continuous contact between the moving parts. However, there are numerous disadvantages to cord reels utilizing moving contacts. Such reels have a propensity to spark, making them unsuitable for hazardous or wet environments. Furthermore, while high voltage applications maintain sufficient connection between moving contacts, low voltage applications are less able to clear or bypass gaps, dirt, or debris, thereby frequently causing insufficient contact, especially over repeated use.
A second type of retractable cord reel has been developed that maintains a constant connection between the retractable and stationary ends of the cord without the use of brushes. The reel illustratively contains a spool divided into two chambers: one for holding a round retractable cord, and a second, expansion chamber holding a coil of flat cord that can be expanded within the reel housing. (Some cord reels have used a flat retractable cable but it is much less tolerant to twisting. Attempts have been made to use a round cord as the stationary expanding cord but it is inefficient and prone to jamming. The flat/round combination is the preferred embodiment.) The retractable cord is connected to the stationary end through an internal coil, which may expand through its chamber during rotation of the spool. An example of this type of reel is disclosed in U.S. Pat. No. 5,094,396 to Burke, the disclosure of which is hereby incorporated by reference.
The expansion cord length may be minimized by permitting expansion of the cord followed by a reverse-direction contraction of the cord. This process is illustrated in U.S. Pat. No. 6,372,988 to Burke, the disclosure of which is hereby incorporated by reference.
While these earlier approaches improved upon the prior art, such designs still left a number of problems in operation. For instance, prior multi chamber designs lack the ability to prevent the stationary expanding cord from being severely bent during reverse direction coiling. This movement may be analogized to the bending of a wire coat hanger where bending it at a large angle back and forth repeatedly will cause it to break. Similarly, in existing cord reel assemblies, the mechanical strain from the repeated severe, back and forth bending of the stationary expanding cord resulting from its reversing coiling direction creates a significant risk to the longevity of such cord reel assemblies. Thus, there is a need to provide a mechanism which reduces mechanical strain resulting from severe sharp bending angles in the operation of a stationary expanding cord inside a cord reel assembly. The present invention is directed toward allowing coiling without sharp or small radius bending, as occurred in the prior art. For instance, the present invention controls the minimum radius at which the wire will bend, that radius being controlled by the winding surface, as opposed to the prior art, in which the coil was exposed to a sharp, near zero radius bend thus producing strain and premature failure. Likewise, prior art cord reel assemblies employing the combination of the flat expanding cord and the round retractable cord create manufacturing problems which make the manufacture of a single unitary cord impractical. Thus, the existing manufacturing techniques call for the flat and round cord segments to be spliced together, such splicing can potentially create hazards to the longevity of the product, especially in operating environments which are corrosive or under operating conditions which could cause shorting or similar problems. Thus, there is a need to reduce or eliminate hazards from shorting or other problems resulting from adverse operating environments while not adversely impacting the manufacturing process related to such cord reel assemblies.
Furthermore, existing prior art cord reel assemblies provide a limitation on the current available for the operation of the assemblies, as the cords (especially the stationary, expanding flat cord) generate significant amounts of heat in relation to the current being carried. Thus, there is need for an improved configuration and design which enables improved heat dissipation for the stationary, expanding flat cord in such assemblies.